refactor(usb/phy): Merge P4 and S2/S3 PHYs into one module

P4 had separate PHY implementation for initial bring-up,
now we can merge it with the original PHY driver.

components/usb/test_apps/phy/pytest_usb_phy.py

@@ -8,6 +8,5 @@ from pytest_embedded import Dut
 @pytest.mark.esp32s3
 @pytest.mark.esp32p4
 @pytest.mark.generic
-@pytest.mark.temp_skip_ci(targets=['esp32p4'], reason='P4 PHY not yet migrated')
 def test_usb_phy(dut: Dut) -> None:
     dut.run_all_single_board_cases(group='phy')